This invention relates to an apparatus for repairing a pattern film of a photomask, a reticle, semiconductor, etc.
FIG. 2 shows a conventional apparatus for repairing a pattern film. Ions, which are generated from an ion source 1, pass through an ion optical system including a focusing lens 2 and an objective lens 3 and are formed into a focused ion beam 5 having a predetermined radius (of not more than 1 micrometer). The focused ion beam 5 passes through a scanning electrode 4 and scans across a surface of a sample 6.
An excess portion of a pattern film formed on the surface of the sample 6 is positioned directly below the focused ion beam by moving an XY stage 7 on a basis of preset data and/or secondary charged particles 8 emitted from the surface of the sample by the irradiation with the scanning focused ion beam 5 which secondary charged particles are detected by means of a secondary charged particle detector 9. The output from the secondary charged particle detector 9 passes through an electronic circuit such as an A/D converter 10 so that a pattern of detected secondary charged particles 8 is displayed on a display device 11. The displayed pattern is observed and recognized by the naked eye, and then the sample 6 is moved by controlling the XY stage 7 so that the excess portion of the pattern film comes within the focused ion beam 5 scanning range.
The position and the range of the excess portion of the pattern film is defined by the display of the display device 11, and then the range of the excess portion of the pattern film is irradiated with the scanning focused ion beam by controlling the scanning electrode 4 and/or blanking electrode 12 (i.e., deflecting the ion beam out of the sample so that it will not reach the sample). In this way, only the excess portion of the pattern is repeatedly irradiated with the scanning focused ion beam so that the excess portion of the pattern film is removed by means of sputtering (sputter etching) effected by ions.
The fact, that in the conventional photomask repairing apparatus, an opaque defect is repaired (removed) by means of sputtering (sputter etching) with a scanning focused ion beam alone, causes the following problems. When an opaque defect on a photomask is repaired by sputter etching alone, gallium remains on the surface of the substrate due to irradiation by the scanning focused ion beam (gallium ions in most cases) and the transparency of the repaired portion of the opaque defect is reduced. Additionally, the surface repaired by means of sputter etching is not perfectly smooth so that it reflects light diffusively, and thus the transparency of the repaired portion of the opaque defect is reduced. In addition to the above, when a pattern film is a multi-layered film of chrome and chrome oxide, the boundary layer between the substrate and a chrome layer or a chrome oxide layer or a chrome layer and a chrome oxide layer changes the intensity of the secondary charged particles so that it is difficult to judge when an opaque defect repair is completed. Because this happens, an opaque defect repair may not be completed or may continue until unwanted damage of the substrate may be caused. Thus, the reliability of opaque defect repair is not high. Further, the material of a pattern film formed on a substrate and subjected to sputter etching is sputter-deposited on the rise portion formed at the removed area of the pattern film or on the periphery thereof. This results in the problem that the sharpness of the sputter etched edge is degraded.